Purpose: :
The photopic ERG has a luminance-response curve which showsb-wave amplitudes increasing to a maximum, and then decreasingto reach a non-zero plateau. This asymptotic luminance-responsefunction has been referred to as the "Photopic Hill". The Photopichill has been shown in primates to result from luminance dependentinteraction of cone on- and off-responses. Recently, the Photopichill has been modeled by the sum of a Gaussian function anda logistic growth function using a 16 step protocol (Hamiltonet al. 2007) and has been tested in a small number (n=7) ofpatients. Herein we describe a photopic hill protocol usingfewer steps which yields results that fit a combined Gaussian-logisticmodel and which are in good agreement with results previouslyobtained by Hamilton et al.

Methods: :
Thus far Photopic hills have been obtained from 9 eyes of 6normal subjects with dilated pupils using DTL fiber electrodesand an Espion e2 system (Diagnosys LLC), with background: 30cd.m-2; flash stimuli: -1.2 to 3.0 log cd.sec.m-2 in eight steps.Two artifact-free ERGs were averaged at each step and b-waveamplitude values were fitted using a non-linear regression analysis(SigmaPlot v11.0).

Conclusions: :
The human Photopic hill is well described by a combined Gaussianand logistic growth function. We have developed a brief protocoltaking 5 minutes which can be used to generate a combined Gaussian-logisticfunction that compares favorably with the Hamilton et al. modelin normal subjects. Clinical utility of this protocol is underinvestigation.